|MadSci Network: Astronomy|
Interesting question, Rod. Sunlight does refract through Earth's atmosphere but it's filtered and diffused by the atmosphere's thickness and varying density. When you see a total lunar eclipse, you often see the moon turn blood red--this is from the sunlight that passes through the atmosphere around the edge of the Earth as seen from the moon. It's the same kind of reddened light you see during a sunrise or sunset. In fact, the Moon is red during a lunar eclipse from the light of all the sunsets and sunrises happening on Earth at once. Another factor to consider is just how thin the atmosphere is with respect to the Earth. Although the "top" of the atmosphere is considered to be at about 75 miles, most of the the air is in the densest part within 20,000 feet of the surface. This is why mountain climbers need extra oxygen. So the part of the atmosphere that refracts sunlight the most is so thin compared to the Earth that very little sunlight is getting refracted into the area behind the Earth, compared to the amount of sunlight blocked by the Earth itself. Even if you traveled far enough behind the Earth to be beyond the umbra (the cone of shadow where direct sunlight is blocked completely) you'd still be in the penumbra where the Earth is partially obscuring the Sun. And the amount of sunlight being obscured by the Earth would always be bigger than the amount of sunlight passing through the atmosphere. The best bet for Space Solar Power is to put your power satellite somewhere where it won't be eclipsed by the Earth or the Moon very often so you get as much raw, direct sunlight as possible. Hope that helps you plan your mission. Best, -Adams Douglas Senior Developer Dicon Inc.
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